194002894 - Y054 P0685 - MAIN RELAY (UNEXPECTED INTERVENTION)

The diagnostic equipment signals: Error P0685 (main relay), with detail "unexpected intervention"
This error is detected if the main relay switches off too quickly. If the main relay switches off too quickly during a period of inactivity for the control unit, the fault codes will not be memorized.
0Preliminary checksALL OKPROBLEMS ENCOUNTEREDACTION
Select the following system on the diagnostic equipment: EDC16C39 Diesel electronic injection system. Delete the errors present and turn the ignition key OFF. Wait until the engine management control unit switches off (min. 20 seconds.). Note: The main relay is switched off. If the engine is very hot, the fans remain on after the ignition is switched off. In this case, the control unit switches off automatically 10 secs after the fans are switched off.Move on to Step 1
1Check on operation of main relayALL OKPROBLEMS ENCOUNTEREDACTION
Errors check. Drive the vehicle in different driving conditions (engine speed and engine load) for a long stretch. Listen out for unusual noises and other system irregularities. At the end of the road test, check that none of the following errors is present using the diagnostic equipment:

  • P0335 - Engine rpm sensor, with detail "signal not valid"
  • P0606 - Control unit broken (microprocessor)
  • P1618 – Control unit broken (HW CY940)
End of diagnosis1.The engine is not running smoothly1.Proceed as instructed in the fault diagnosis    See table D003 ENGINE NOT RUNNING SMOOTHLY / (IRREGULAR OPERATION)
2.The engine is losing power1.Proceed as instructed in the fault diagnosis    See table D004 FRONT/ENGINE COUPLING
3.The engine does not produce maximum performance1.Proceed as instructed in the fault diagnosis    See table D005 ABS COUPLING
4.The engine response is poor1.Proceed as instructed in the fault diagnosis    See table D016 ADDITIONAL DASHBOARD/LEFT FRONT DOOR COUPLING
5.There is engine knock1.Proceed as instructed in the fault diagnosis    See table S003 ENGINE KNOCKING
6.Error P0335 is present1.Proceed as instructed in the test    See Test 1060GI ENGINE SPEED CHECK
7.Error P0606 is present1.Proceed as instructed in the testSee Test 1060GK CONTROL UNIT SOFTWARE AND HARDWARE CHECK
8.Error P1618 is present1.Proceed as instructed in the test    See Test 1060GL CHECK ON OPERATION OF ENGINE MANAGEMENT CONTROL UNIT MAIN RELAY